234 



SELECTION. 



Chap. XXI, 



I 



pigeons, &c, of the same race, have been separately bred during 

 a number of years by different men without any wish on their 

 part to modify the breed. We see the same fact in the differ- 

 ence between hounds bred for hunting in different districts, 39 

 and in many other such cases. 



In order that selection should produce any result, it is 

 manifest that the crossing of distinct races must be prevented • 

 hence facility in pairing, as with the pigeon, is highly favourable 

 for the work; and difficulty in pairing, as with cats, prevents 

 the formation of distinct breeds. On nearly the same principle 

 the cattle of the small island of Jersey have been improved in 



their milking qualit 



ith 



-pidity 



could not have 



been obtained in a widely extended country like France."^ 

 Although free crossing is a danger on the one side which 

 every one can see, too close interbreeding is a hidden danger 

 on the other side. Unfavourable conditions of life overrule the 

 power of selection. Our improved heavy breeds of cattle and 



sheep could not have been formed on mount 



pastures 



nor could dray-horses have been raised on a barren and inhos 



pitable land, such 



the Falkland islands, where even the 



light horses of La Plata rapidly decrease in size. Nor could 

 the wool of sheep have been much increased in length ™'+ 1 -- 



The 



long and short beaked 



the Tropics ; yet selection has kept Merino sheep nearly 

 under diversified and unfavourable conditions of life, 

 power of selection is so great, that breeds of the dog, sheep, and 

 poultry, of the largest and least size, 



pigeons, and other breeds with opposite characters, have had 

 their characteristic qualities augmented, though treated in every 

 way alike, being exposed to the same climate and fed on the 

 same food. Selection, however, 

 by the effects of use or habit. 



either checked 



favoured 



Our wonderfully-improved pigs 

 could never have been formed if they had been forced to search 

 for their own food ; the English racehorse and greyhound could 



been improved up to their present high standard of 





excellence wwuim „ 



As conspicuous deviations of structure occur 



provement of each breed 



the 



•ally the result, as already 



39 ' Encyclop. of Kural Sports,' p. 405. 



40 Col. Le Couteur, < Journal Roy. Agricult. Soc.,' vol. iv. p. 43. 



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